1. Field of the Invention
The present invention generally relates to image forming apparatuses that shift a scanning position on a surface scanned of each of a plurality of optical beams to a main scanning direction and a sub-scanning direction, and at the same time, simultaneously scan a plurality of lines in the main scanning direction by a deflector.
2. Description of the Related Art
Conventional methods of correcting a starting position for writing (hereinafter referred to as a “writing start position”), of each beam in this kind of a multi-beam image forming apparatus are proposed in Japanese Laid-Open Patent Applications No. 6-300980, No. 9-66630, No. 10-68900 and No. 11-194238, for example.
In order to realize a faster digital laser printer, a faster multi-beam polygon motor is required. In a system where multi-beams are used and the writing start position of each beam is determined according to a synchronizing signal obtained from each light emission, concurrently with the speeding up of the polygon motor, the interval between incident beams is becoming shorter.